Conventionally, rotary surface treating apparatuses have been used as tools for conducting high-quality plating on fine components (small elements) illustrated in FIG. 15 (patent documents 1 through 4).
In other words, a rotary surface treating apparatus comprises a rotatable treatment container having a solution outflow part on at least a part of circumference thereof and having a cathode on the circumference thereof, a dome part surrounding the treatment container and an anode inserted from an upper opening of the container, wherein the following steps such as surface treatment solution and the treatment object are housed in the container, the treatment object is pushed so as to cover a cathode with the treatment object as a result of centrifugal force caused by rotating such container while providing the surface treatment solution, the surface treatment solution is splattered from the solution outflow part and is collected within the dome part, and thereby the surface treatment solution within the container is updated.
The apparatus is used under the condition of energizing the anode and the cathode while supplying plating solution as the surface treatment solution when plating is carried out on a treatment object, and that is used under the condition of supplying into the container the surface treatment solution such as cleaning water and pre-treatment solution without carrying out energization when washing and pre-treatment are carried out.
FIG. 15 are diagrams illustrating examples of small elements that become the object of plating treatment on the rotary surface treating apparatus in which plated portions are illustrated in dashed lines EP1 to EP3. FIG. 15A shows a chip capacitor made of rectangular shaped ceramics and both ends thereof being plated (EP1). FIG. 15B is an enlarged partial cross sectional view of a particle of plating powder for double plated (EP2, EP3) BGA on the surface of powdered material (plastic material and steel product) having diameter 0.1 to several mm.
In order to carry out uniform thick plating on a desired portion of a relatively small treatment object, it is suitable to make the treatment object under the condition of moving the object toward the circumference direction by rotating the container housing the plating solution and the object therein and to carry out electroplating by energizing between the anode disposed on the center of the container and the cathode arranged on the circumference direction under the previous condition.
General mechanisms of rotary plating treatment carried out in the rotary surface treating apparatus will be described in below using FIG. 16.
As shown in FIG. 16, a Plating treatment part that carries out rotary plating treatment comprises a treatment container T0 having circular cathodes N0 and is attached to a rotation drive shaft S0, an anode P0 immersed in plating solution, a dome part R0 collecting the plating solution splattered from a solution outflow part H0. The anode P0 is arranged such that it is immersed in the plating solution at the center of the circularly formed container T0, and plating treatment is carried out by energizing under the condition of covering the circular cathode with treatment objects W that are moved toward the circumference direction by rotating the container as shown in FIG. 16. Since fine pores or slits impenetrable to the objects W are formed on the solution outflow part H0 with porous-rings, channels, washers and the like, immersed plating solution is always splattered circumferentially, but such solution is collected by the dome part R0 and feedbacks to the container T0 (refilled from a solution supply pipe Q0 of an upper opening Z0), so that the plating solution within the container always circulates.
The container not only rotates in forward direction, but also repeatedly rotating in the reverse direction, decelerating its speed and stopping its rotation for stirring the treatment objects, thereby uniform plating quality can be achieved.
FIG. 17 shows a series of operation in the plating treatment. FIG. 17 is a flow chart of each treatment in the plating treatment. As shown in FIG. 17, in electroplating treatment, plating accustomization operation S02, plating operation S04 and plate dewatering operation S08 are carried out, and then washing accustomization operation S09, washing operation S10 and washing dewaterization operation S11 are carried out in that order as treatments for washing the objects W and the container T0. Alternatively, further washing treatment may be carried out prior to the plating accustomization operation S02. As shown in FIG. 17, defoaming operation S06 may appropriately be carried out during the plating operation S04.
The plate accustomization operation S02 shown in FIG. 17 is carried out in order to accustom the objects W to the plating solution. This is to prevent insufficient contact of the objects W to the cathode(s) of periphery of the container and to prevent overflow of the objects from the upper surface of the plating solution when the objects are powder such as very fine particles, because they do not accustom to the plating solution due to very light weight for each of them and these particles flow on the surface of the plating solution by centrifugal force.
In the plating operation S04 shown in FIG. 17, plating treatment is carried out by energizing through a rectifier (FIG. 16) under the condition of pushing the objects W toward the circular cathodes N0 by centrifugal force in accordance with operating condition parameters input by the operator.
In the defoaming operation S06 shown in FIG. 17, such operation is carried out under the condition of decreasing the rotation speed and floating foams on the surface in order to remove the foams. In practice, such operation is carried out on a mandatory basis by invalidating a level sensor (not shown) and outflowing the plating solution from the upper opening Z0 (FIG. 16). Here, the reason for occurring foams is one of that the plating solution becomes foamy as a result of air to be mixed into the plating solution by stirring the objects because surface acting agent is contained in the solution and that that the plating solution becomes foamy as a result of hydrogen gas generated during electroplating.
In the plate dewatering operation S08 shown in FIG. 17, supply of the plating solution is suspended under the rotation of the container and the solution is discharged. No reverse rotation is carried out in the plate dewatering operation S08 and the washing dewaterization operation S11 in order to avoid damages on the treatment objects W.
Even in the above-described operation, it is important to reach appropriate operating conditions in order to carry out desired plating on the treatment object because various parameters such as the number of constant rotation of the container during the plating treatment, acceleration period reaching to the constant rotation speed, the amount of energization and so forth vary depending on a variety of conditions such as shape of the object, position of plating, fluidity of the solution and so forth.    Patent Document 1: Patent laid-open publication No. 2006-037184    Patent Document 2: Patent laid-open publication No. Hei 08-239799    Patent Document 3: Patent laid-open publication No. Hei 07-118896    Patent Document 4: Patent laid-open publication No. Hei 09-137289